The present invention relates to a new and improved apparatus for soldering printed circuit or wiring boards carrying circuit components.
Generally speaking, the soldering apparatus for printed circuit boards of the present invention is of the type comprising a solder bath and a number of transport frames moved by a conveyor device. Each of the transport frames is structured for receiving a circuit board upon which there have been placed the circuit components. The transport frames are guided at their leading corners and at their trailing corners by related guide tracks. These guide tracks, at the region of the solder bath and, viewed in the direction of the conveying of the transport frames, possess respective descending ramps and following thereat respective ascending ramps.
In the context of this disclosure there is to be understood under the expression "soldering printed circuit boards carrying circuit components" that there are soldered the connection leads or wires of active circuit components which are mounted at one side or face of a prepared printed circuit board. Soldering is accomplished at that location where the connection leads or wires protrude out of the other side or face of such circuit board. These connection leads or wires, also referred to in the art sometimes as "legs", have different lengths, so that at the side of the printed circuit board facing away from the circuit components or elements, there is formed a so-to-speak "lead tuft", where the individual connection leads or wires are arranged more compactly next to one another the smaller the circuit components are, on the one hand, and the more compact the circuit components are arranged upon the printed circuit board, on the other hand.
As will be readily appreciated it is not simple to solder such a "lead or wire tuft" in one working operation such that each of the protruding connection leads or wires has been positively soldered only at its location where it piercingly extends through the printed circuit board and only at such location.
If the immersion of the printed circuit board into the solder bath is accomplished parallel to itself and to the surface of the solder bath, for instance by lowering the printed circuit board or by raising the solder bath, then the danger exists that air bubbles will be caught in the "lead tuft", and therefore, hinder soldering of one or the other connection lead or wire. This defect, as mentioned, can be somewhat counteracted if the immersion of the printed circuit board into the solder bath is accomplished with a forward tilting movement of the printed circuit board, so that initially the leading region of the underside or face of the printed circuit board is immersed into the solder bath and only thereafter the trailing region. In this way it is possible to afford sufficient time for air encaptured in the "lead tufts" to possibly escape.
On the other hand, particularly in the case of long, protruding and/or densely arranged connection leads or wires it is important to prevent that, upon lifting the printed circuit board out of the solder bath, solder tabs or bridges will not remain hanging at such connection leads or wires. Should such occur, then it is possible that there are formed undesired electrical connections between connection leads or wires which otherwise should remain insulated from one another.